1. Chapter 7 Earth

2. Mantle Two-part core Thin crust Hydrosphere (oceans) Atmosphere Magnetosphere Structure of Planet Earth

3. Troposphere is where convection takes place Responsible for weather Earth’s Atmosphere

4. Convection depends on warming of ground by the Sun Earth’s Atmosphere

5. Ionosphere is ionized by solar radiation and is good conductor Reflects radio waves in the AM range, but transparent to FM and TV Ozone layer is between ionosphere and mesosphere; absorbs ultraviolet radiation Earth’s Atmosphere

6. Chlorofluorocarbons (CFCs) have been damaging the ozone layer, resulting in ozone hole Earth’s Atmosphere

7. Surface heating: Sunlight that is not reflected is absorbed by Earth’s surface, warming it Surface re-radiates as infrared thermal radiation Atmosphere absorbs some infrared, causing further heating Earth’s Atmosphere

8. This is known as the greenhouse effect Earth’s Atmosphere

9. Scattering of light by air depends its wavelength Wavelength of blue light is closer to the size of air molecules So it is scattered most strongly Why Is the Sky Blue?

10. History of Earth’s atmosphere: Primary atmosphere was hydrogen, helium; this escaped Earth’s gravity Secondary atmosphere, from volcanic activity, mostly nitrogen Life appeared, creating atmospheric oxygen Earth’s Atmosphere

11. The Greenhouse Effect and Global Warming Result of modern society has been to increase CO 2 levels Corresponding increase in global average temperature

12. The Greenhouse Effect and Global Warming Some possible consequences of global warming: Rise in sea level More severe weather Crop failures (as climate zones change) Expansion of deserts Spread of tropical diseases away from the tropics

13. Seismic waves: Earthquakes produce both pressure and shear waves. Pressure waves are longitudinal and will travel through both liquids and solids. Shear waves are transverse and will not travel through liquid, as liquids do not resist shear forces. Wave speed depends on the density of the material. Earth’s Interior

14. We can use the pattern of reflections during earthquakes to deduce interior structure of Earth Earth’s Interior

15. Currently accepted model: Earth’s Interior

16. Mantle is much less dense than core Mantle is rocky; core is metallic—iron and nickel Outer core is liquid; inner core is solid, due to pressure Volcanic lava comes from mantle, allows analysis of composition Earth’s Interior

17. Earth’s “Rapidly” Spinning Core Analysis of seismic waves shows inner core rotating slightly faster than rest of Earth—about 1° faster per year.

18. Earth’s Interior History Probably molten when formed Remelted due to bombardment by space debris Heavier materials sank to the center Radioactivity provides a continuing source of heat.

19. Continental drift: Entire Earth’s surface is covered with crustal plates, which can move independently Surface Activity

20. At plate boundaries, get earthquakes and volcanoes Surface Activity

21. Earth’s upper mantle, near a plate boundary; this is a subduction zone, where one plate slides below another Surface Activity

22. A plate colliding with another can also raise it, resulting in very high mountains Surface Activity

23. Plates can also slide along each other, creating faults where many earthquakes occur Surface Activity

24. Finally, plates can move away from each other, creating rifts Surface Activity

25. New crust created at rift zones preserves the magnetic field present at the time it solidified Field reversals occur about every 500,000 years. Surface Activity

26. Radioactive Dating # of protons in an atom’s nucleus determines the element Different isotopes of the same element, with the same # of protons w/different #s of neutrons Many are unstable and undergo radioactive decay Decay is characterized half-life T :

27. Radioactive Dating This plot shows the fraction of the original sample remaining as a function of time

28. Radioactive Dating Half-lives have been measured in the laboratory for almost all known isotopes. The most useful isotope for dating rock samples is uranium-238, which has a half- life of 4.5 billion years, comparable to the age of the Earth.

29. Radioactive Dating The dating process involves measuring the ratio between the parent nucleus and the daughter nucleus (lead-206 in the case of uranium-238)

30. Plate motion is driven by convection Surface Activity

31. Follow the continental drift backwards, the continents merge into one, called Pangaea Surface Activity

32. The magnetosphere is the region around the Earth where charged particles from the solar wind are trapped Earth’s Magnetosphere

33. Charged particles trapped in the Van Allen belts, where they spiral around the magnetic field lines Earth’s Magnetosphere

34. Near the poles, the Van Allen belts intersect the atmosphere. The charged particles can escape; when they do, they create glowing light called aurorae. Earth’s Magnetosphere

35. Tides are due to the gravitational force on Earth from moon The Tides

36. The Sun has less effect because it is farther away, but it does modify the lunar tides The Tides

37. Tides tend to exert a “drag” force on the Earth, slowing its rotation. This will continue until the Earth rotates synchronously with the Moon, so that the same side of the Earth always points toward the Moon. The Tides